Display apparatus

ABSTRACT

A display apparatus capable of displaying a picture with halfbrightness (gray scale) by use of a display panel such as a plasma display panel, comprising a plurality of picture elements or luminescent dots which assume either a luminescent condition or a nonluminescent condition. A halftone picture display can be achieved according to two methods, the first being that the mean brightness of the picture element or luminescent dot be made porportional to the turn-on period. The second method is that the mean brightness of the picture element or luminescent dot for the turn-on period be made proportional to the frequency of the sustaining voltage. Several embodiments are disclosed which incorporate one or both of the foregoing principles to achieve a halftone display.

United States Patent Kurahashi et a1.

[ Sept. 16, 1975 DISPLAY APPARATUS Assignee:

Mitsubishi Denki Kabushiki Kaisha,

Tokyo, Japan Filed:

Sept. 19, 1973 App]. No.: 398,791

3,575,492 4/1971 Nester et a1 340/324 UX 3,590,156 6/1971 315/169 TV 3,659,149 4/1972 315/169 TV 3,778,673 12/1973 Eisenberg' et a1. 315/169 R Primary ExaminerMichael J. Lynch Assistant Examiner-B. P. Davis Attorney, Agent, or Firm-Oblon, Fisher, Spivak, McClelland & Maier [5 7 ABSTRACT A display apparatus capable of displaying a picture with half-brightness (gray scale) by use of a display panel such as a plasma display panel, comprising a plurality of picture elements or luminescent dots which assume either a luminescent condition or a nonluminescent condition. A halftone picture display can be achieved according to two methods, the first being that the mean brightness of the picture element or luminescent dot be made porportional to the turn-on period. The second method is that the mean brightness of the picture element or luminescent dot for the turn-on period be made proportional to the frequency of the sustaining voltage. Several embodiments are disclosed which incorporate one or both of the foregoing principles to achieve a halftone display.

26 Claims, 40 Drawing Figures PATENIEBSEP isms 3. 896.290 sum 1,

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PATENTEU SEP 1 6 I975 S'riEET FIGS PATENTED SEP 1 6 I975 SHEET PATENTED SEP 1 6 I975 FIG.2I

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PATENTEB SE? is ms SHEET F I G 26 

1. A display apparatus comprising a display panel having a plurality of luminescent dots each assuming either a luminescent state or a nonluminescent state, at least one of said luminescent dots constituting each of a pluraliTy of picture elements disposed on said display panel; and a control device for controlling the luminous state of each of said picture elements according to the video signal to be displayed on said display panel; wherein said control device is operated so that each of said picture elements is turned on with a mean brightness proportional to the instantaneous value of said video signal; the control device being operated so that the instantaneous value V of said video signal corresponding to each of said picture elements is coded by the use of n weights w1, w2, w3 ..., wn, according to the formula V K(a1w1 + a2w2 + a3w3 + ... + anwn) where a1, a2, a3, ..., an represents a value of 1 or 0, and K represents a conversion constant; and wherein each of said picture elements is turned on with a mean brightness proportional to the weight wk corresponding to the condition ak (k 1, 2, 3, ..., n).
 2. The display apparatus in accordance with claim 1, further comprising a coder operated so that said instantaneous value V of said video signal corresponding to each of said picture elements is coded by the use of n weights w1, w2, w3, ..., wn, according to said formula.
 3. The display apparatus in accordance with claim 1, wherein each of said picture elements comprises a plurality of luminescent dots adjacent to each other.
 4. The display apparatus in accordance with claim 1, wherein said control device controls the turn-on period of each of said luminescent dots so that each of said picture elements is turned on with a mean brightness proportional to the weight wk corresponding to the condition ak 1 (k 1, 2, 3, ..., n).
 5. A display apparatus comprising: a display panel having picture elements each having a turn-on state and a turn-off state; a coder for coding the instantaneous value V of the video signal corresponding to each of said picture elements for display on said display panel by use of n weights w1, w2, w3, ..., wn, according to the formula V K(a1w1 + a2w2 + a3w3 + ... + anwn) where a1, a2, a3, ..., an represent the value of 1 or 0 and K represents a conversion constant; and a control device operated so that the picture element in the state, ak 1, in the k-th frame (k - 1, 2, 3, ..., n) contained in one period consisting of n consecutive frames is turned on, and so that the time interval between the turning on and off of said picture element is proportional to said weight wk.
 6. The display apparatus in accordance with claim 5, further comprising a display panel with picture elements two-dimensionally disposed in both the horizontal and vertical directions, each of said picture elements assuming a bistable state as it is turned on by a turn-on pulse and turned off by a turn-off pulse; a turn-on scanning circuit having shift registers for vertical scanning and for controlling the generation of said turn-on pulse; a turn-off scanning circuit with shift registers to which the first stage thereof the output of a specific state of said turn-on scanning circuit is supplied and thus controls the generation of said turn-off pulse; and a gate circuit for switching, frame by frame, the output stage of said turn-on scanning circuit for the input to the first stage of said turn-off scanning circuit.
 7. A display apparatus comprising: a display panel having picture elements each capable of assuming two states, a turn-on state and a turn-off state; a coder for coding the instantaneous value V of the video signal corresponding to each of said picture elemeNts for display on said display panel by the use of weights w1, w2, w3, ..., wn, according to the formula V K(a1w1 + a2w2 + a3w3 + ... + anwn) where a1, a2, a3, ..., an represent the value of 1 or 0 and K represents a conversion constant; and a control device operated so that the picture element in the state, ak 1, in the k-th frame (k 1, 2, 3, ... n) contained in one period consisting of n consecutive frames is turned off, and so that the time interval between the turning off and on of said picture element is proportional to said weight wk.
 8. A display apparatus comprising: a display panel having picture elements each assuming two states, a turn-on state and a turn-off state; a coder for coding the instantaneous value V of the video signal corresponding to each of said picture elements for display on said display panel, by the use of weights w1, w2, w3, ..., wn according to the formula V K(a1w1 + a2w2 + a3w3 + ... + anwn) where a1, a2, a3, ..., an represent the value 1 or 0 and K represents a conversion constant; and a control device operated so that the codes a1, a2, a3, ..., an provided by said coder are assigned to at least one but not more than n frames, and so that the picture element in the state, ak 1, (k 1, 2, 3, ..., n) for the assigned code ak, in each frame is turned for a period proportional to said weight wk.
 9. A display apparatus comprising: a display panel having picture elements each assuming two states, a turn-on state and a turn-off state; a coder for coding the instantaneous value V of the video signal corresponding to each of said picture elements for display on said display panel, by the use of weights w1, w2, w3, ..., wn, according to the formula V K(a1w1 + a2w2 + a3w3 + ... + anwn) where a1, a2, a3, ..., an represent the value of 1 or 0 and K represents a conversion constant; and a control device operated so that the picture element in the state, ak 1(k 1, 2, 3, ..., n), is turned on a length of time equal to
 10. The display apparatus in accordance with claim 8, wherein said picture elements are turned on and off in the ascending order or in the descending order of said weights wk.
 11. The display apparatus in accordance with claim 8, further comprising: a plurality of X electrode lines and a plurality of Y electrode lines two-dimensionally disposed on said display panel and having said picture elements located at the intersections of said X and Y electrode lines; first, second, third, ..., n-th and (n + 1)-th scanning circuits each having shift registers for scanning said Y electrode lines; and a control device operated so that the output of a specific stage of the N-th scanning circuit (N 1, 2, 3,000, n) or of the first scanning circuit is supplied to the first stage of the (N + 1)-th scanning circuit, and so that the application of a turn-on pulse to said Y electrode lines is controlled by the output Of said N-th scanning circuit, and the supply of a turn-off pulse to said Y electrode lines is controlled by the output of said (N + 1)-th scanning circuit.
 12. The display apparatus in accordance with claim 8, further comprising at least (n - 1) delay circuits, each having a time delay equal to
 13. The display apparatus in accordance with claim 8, further comprising an analog image memory provided with at least one write head for writing therein the video signal or a signal corresponding to the video signal, and at least (n - 1) first, second, third, ..., (n - 1)-th read heads for reading the written signal therefrom; wherein the time delay interval between the signal read by the (N - 1)-th read head (N 1, 2, 3, ..., (n-1)) and that read by the N-th read head is equal to the time Tk proportional to said weight wk.
 14. The display apparatus in accordance with claim 8 further comprising an analog image memory provided with at least one write head for writing therein the video signal or a signal corresponding to the video signal, and at least n first, second, third.,... n-th read heads with a total delay time equal to said frame period; wherein the delay time interval between the signal read by the N-th read head (N 1,2,3,...,n) and that read by the (n + 1)-th read head is equal to the time Tk proportional to said weight wk.
 15. The display apparatus in accordance with claim 8, further comprising: at least n first, second, third,..., n-th coders each capable of making a coded output and a residual analog output available when the analog input is above a given level, or making the analog input or an output corresponding to the analog input available when the analog input is below the given level; and an analog image memory provided with at least (n - 1) pairs or write and read heads for writing the residual output signal of the N-th coder (N 1, 2, 3, ..., (n - 1)) or a signal corresponding to the residual output signal and for reading the written signal with a delay Tk proportional to said weight wk wherein the output of the (n - 1)-th read head is supplied to the n-th coder.
 16. A display apparatus comprising: a display panel with a plurality of luminescent dots each assuming two states, a luminescent state effected by a turn-on pulse and a non-luminescent state effected by a turn-off pulse, and each picture element comprising n of said luminescent dots Alpha 1, Alpha 2, Alpha 3, ..., Alpha n; a coder for coding the instantaneous value V of the video signal corresponding to each of said picture elements for display panel, by the use of weights w1, w2, w3, ..., wn, according to the formula V K(a1w1 + a2w2 + a3w3 + ... + anwn) where a1, a2, a3, ... an represent the value of 1 or 0 and K represents a conversion constant; and a luminescence control device operated so that of n of said luminescent dots, only the one Alpha k corresponding to the condition ak 1 is made luminous in proportion to said weight wk (k 1, 2, 3, ..., n) for a period shorter than the frame period of said video signal.
 17. A display apparatus in accordance with claim 16, further comprising: a plurality of X electrode lines and a plurality of Y electrode lines two-dimensionally disposed on said display panel having said picture elements located at the intersections of said X and Y electrode lines; first, second, third, ..., n-th and (n + 1)-th scanning circuits each having shift registers for scanning said Y electrode lines; and a control device operated so that the output of a specific state of the N-th scanning circuit (N 1, 2, 3, ..., n) or the first scanning circuit is supplied to the first stage of the (N + 1)-th scanning circuit, and so that the application of a turn-on pulse to said Y electrode lines is controlled by the output of said first scanning circuit, and the application of a turn-off pulse to said Y electrode lines is controlled by the output of said N-th scanning circuit.
 18. A display apparatus comprising a plurality of picture elements each capable of being luminous with a luminescent output substantially proportional to the frequency of a sustaining AC voltage during the turn-on period, said picture elements caused to undergo repeating frame scanning wherein n consecutive frames constitute one period, and wherein the video signal V is coded by the use of n weights w1, w2, w3, ..., wn, according to the formula V K(a1w1 + a2w2 + ... + anwn) where a1, a2, a3, ..., an represent the value of 1 or 0 and K represents a conversion constant; the picture element in the state, ak 1, in the k-th frame (k 1, 2, 3, ..., n) being given a turn-on period; the frequency of said sustaining AC voltage for the turn-on period being proportional to said weight wk.
 19. The display apparatus in accordance with claim 18, wherein said plurality of picture elements comprise a plurality of X electrode lines and a plurality of Y electrode lines, and further comprising a sustaining voltage whose frequency is constantly f1 which is applied to said X electrode lines by the half cycle at a specific polarity; a sustaining AC voltage whose frequency is f1, f2, ..., fn from one frame to another which is progressively applied to said Y electrode lines by the half cycle at the reverse polarity; whereby the effective frequency of the sustaining AC voltage applied to the picture element which is given a turn-on period in each frame is controlled to be f1, f2, f3, ..., fn in sequence.
 20. The display apparatus in accordance with claim 19, further comprising: a timing circuit which generates a timing signal for providing said reverse half cycle sustaining AC voltage at frequencies f1, f2, ..., fn; a gate circuit for gating said timing signal and generating a timing signal a fk and fk-1 in the k-th frame; a Y electrode line scanning circuit having shift registers; and a drive circuit for selecting the output fk or fk-1 of said gate circuit and for applying a sustaining voltage to said Y electrode lines; wherein the sustaining voltage whose frequency is fk is applied to the electrode lines scanned before the present scanning line, and the sustaining voltage whose frequency is fk-1 is applied to the electrode lines which are to be scanned.
 21. A display apparatus comprising a plurality of picture elements each capable of being luminous with a luminescent output substantially proportional to the frequency of a sustaining AC voltage during the turn-on period, said picture elements being caused to undergo repeating frame scanning wherein n consecutive frames constitute one period, and wherein the video signal V is coded by the use of (m + n) weights u1, u2, ... um, and w1, w2, ..., wn, according to the formula
 22. The display apparatus in accordance with claim 21 wherein said plurality of picture elements comprise a plurality of X electrode lines and a plurality of Y electrode lines, and further comprising a sustaining AC voltage whose frequency is constantly f1 which is applied to said X electrode lines by the half cycle at a specific polarity, a sustaining AC voltage whose frequency is f1, f2, ..., fn from one frame to another which is progressively applied to said Y electrode lines by the half cycle at the reverse polarity for the picture element given a turn-on period on the j-th frame (j 1, 2, ..., n), whereby the effective frequency of the sustaining AC voltage applied to the picture element which is given a turn-on period in each frame is made to be f1, f2, ..., fn in succession.
 23. The display apparatus in accordance with claim 22 further comprising: a timing circuit which generates a timing signal for providing said reverse half-cycle sustaining AC voltage at frequencies f1, f2, ..., fn; a gate circuit for gating said timing signal and generating a timing signal at fk and fk-1 in the k-th frame; a Y electrode line scanning circuit having a shift registers; and a drive circuit for selecting the output fk or fk-1 of said gate circuit and for applying a sustaining voltage to said Y electrode lines; wherein the sustaining voltage whose frequency is fk is applied to the electrode lines scanned before the present scanning line, and the sustaining voltage whose frequency is fk-1 is applied to the electrode lines which are to be scanned.
 24. A display apparatus comprising a plurality of luminescent dots each capable of being luminous with a luminescent output substantially proportional to the frequency of a sustaining AC voltage during the turn-on period, a plurality of picture elements each comprising a group of m luminescent dots 1, 2, ..., m, wherein consecutive frames constitute one period, and wherein the video signal V is coded by the use of (m + n) weights u1, u2, ..., um and w1, w2, ..., wn, according to the formula
 25. A display apparatus in accordance with claim 24, wherein said plurality of luminescent dots comprise a plurality of X eleCtrode lines and a plurality of Y electrode lines, and further comprising a sustaining AC voltage whose frequency is constantly f1 which is applied to said X electrode lines by the half cycle at a specific polarity; a sustaining AC voltage whose frequency is f1, f2, ..., fn from one frame to another which is progressively applied to said Y electrode lines by the half cycle at the reverse polarity for the luminescent dot given a turn-on period in the j-th frame (j 1, 2, ..., n), whereby the effective frequency of the sustaining AC voltage applied to the luminescent dot which is given a turn-on period in each frame is made to be f1, f2, ..., fn in succession.
 26. A display apparatus in accordance with claim 25 further comprising: a timing circuit which generates a timing signal for providing said reverse half-cycle sustaining AC voltage at frequencies f1, f2, ..., fn; a gate circuit for gating said timing signal and generating a timing signal a fk and fk-1 in the k-th frame; a Y electrode line scanning circuit having shift registers; and a drive circuit for selecting the output fk or fk-1 of said gate circuit and for applying a sustaining voltage to said Y electrode lines; wherein the sustaining voltage whose frequency is fk is applied to the electrode lines scanned before the present scanning line, and the sustaining voltage whose frequency is fk-1 is applied to the electrode lines which are to be scanned. 